The background description provided herein is for the purpose of generally presenting the context of the present invention. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions.
One or more coating layers are generally provided on an outer surface of optical fibers as a protection layer thereof. In a typical process of an optical fiber drawing process, when a preform is collapsed, pulled, and drawn into bare optical fibers, two or more coatings need to be coated online. Generally, a relatively soft inner coating prevents optical fibers from generating microbending and a relatively hard outer coating provides additional protection and a better operability for the optical fibers. The organic polymer coatings can be cured onto an optical fiber surface in manners of heating (heat curing) or ultraviolet irradiation (UV curing). UV curing of an optical fiber coating refers to triggering quick polymerization and crosslinking of liquid-state coating materials on optical fibers by using ultraviolet light, and making the liquid-state coating materials cured into solid materials instantaneously. Ultraviolet curing needs to expose a coating into high-intensity ultraviolet radiation. Improving the ultraviolet intensity can reduce curing time. However, reducing curing time is an important link for improving an optical fiber drawing linear speed so as to improve optical fiber production efficiency.
In a current optical fiber drawing process, a mercury lamp (such as a high-pressure mercury lamp and xenon-mercury lamp) is usually used to generate ultraviolet radiation. When the high-pressure mercury lamp works, currents pass through high-pressure mercury vapors, so that the currents are ionized and excited, thereby forming collision between electrons, atoms, and ions in a discharge tube for light emitting. A disadvantage of the mercury lamp is needing quite large power to generate ultraviolet radiation with sufficient intensity. For example, curing an optical fiber with a single coating layer (such as polymeric coating) may need 50 kw power consumption. Another disadvantage of the mercury lamp is: a large amount of energy for lightening the mercury lamp is emitted out in a form of heat energy rather than ultraviolet light, that is, a utilization rate of the mercury lamp on energy is low. Moreover, because the mercury lamp generates a large amount of heat, a mercury lamp curing device needs to be cooled to prevent the device from overheating.
Furthermore, a spectral width of electromagnetic radiation generated by the mercury lamp is large, including electromagnetic waves with wavelengths less than 200 nm and greater than 700 nm (such as infrared light). Generally, UV radioactive rays with wavelengths between 300 nm and 400 nm can be used for curing, and therefore most of the electromagnetic radiation generated by the mercury lamp is wasted.
With the development of ultraviolet light emitting diode (UVLED) technologies, as a UV radiation source, a UVLED has advantages such as higher energy efficiency, longer life (life of an electrodeless lamp is about 8,000 hours, while life of the UVLED is up to 30,000 hours), a less heating value, less energy consumption, and greater environmental friendliness (mercury is not contained, and ozone is not generated) as compared with the traditional mercury lamp. Applying the UVLED to replace the traditional mercury lamp for optical fiber coating and curing is advantageous. As compared with the traditional mercury lamp, energy needed by the UVLED device is prominently reduced, and less heat is correspondingly generated, and the efficiency is higher in optical fiber coating. However, there still exists an unaddressed need of which, particularly, a UVLED light source cannot perform automatic adjustment on ultraviolet intensity according to a real-time drawing speed and coating condition of optical fibers.